Developing a Projection of Future
Teacher Supply

For a First-Order Projection

Note

19

We noted previously the more detailed discussion of state-level teacher supply and demand projection that can be found in Reichardt (2003). In addition, a particularly illuminating discussion of the many considerations that must be brought to bear in analyzing a state’s supply of science and mathematics teachers can be found in The Critical Path Analysis of California’s Science and Mathematics Teacher Preparation System (2007). Beyond this practical example, the National Research Council, in its 1990 study Precollege Science and Mathematics Teachers: Monitoring Supply, Demand, and Quality, presents a sophisticated methodological discussion of the particular difficulties that attend efforts to estimate teacher supply.

The guidelines¹⁹ offered here for developing a basic projection of teacher supply consist of four suggested steps:

1. Gather baseline data on the teachers who are currently teaching science and mathematics courses throughout the state
• Number of teachers
• Their gender and ethnicity
• Their licensure or certification
  

  Note

  20

  Data about teachers’ licensure or certification status are useful in providing insight into the extent to which a state’s overall teacher workforce – and the workforce in specific districts – has the minimum basic qualifications. The fact that all teachers in a state, district, or school have a valid teaching license is not an assurance, however, that they teach only those classes for which their license and qualifications are appropriate.
  status²⁰ – whether they are fully licensed, their licensure stage (provisional, permanent, advanced, etc.), and the specific subjects and/or courses their license, certificate, or endorsement permits them to teach
• Their age and years of experience in full-time teaching

Elaboration

The calculation of the number of science and mathematics teachers in a state is not uncomplicated. There is the issue, first of all, of whether all teachers teaching science and mathematics courses should be properly counted as science and mathematics teachers. As we note several times throughout this project and discuss in greater detail in the unit on Teacher Quality and Teacher Licensure, we would argue that only teachers who have the appropriate state credentials to teach specific science and mathematics subjects – including those alternate route and in-migrating teachers who have been legitimately granted temporary credentials – should be counted as part of the active science and mathematics teacher supply. Without this restriction, the supply of science and mathematics teachers becomes, if not infinite, then certainly so large and ill-defined that it threatens to make a meaningful analysis of supply and demand and the development of effective policies to address them impossible.

Secondly, the number of teachers is contingent upon the inclusion or exclusion of private schools from the supply calculation. We have chosen to focus on public education in these guidelines, which both narrows the definition of who is included as a teacher and reduces the number of teachers counted in the active supply. (It would increase the number of teachers in the reserve pool, however, because active private school teachers are potential public school employees.)

Still another complication is the fact that individual teachers may have multiple certifications in science and mathematics. Thus, a single individual who teaches both biology and physics, for example, or both natural science and mathematics, may be double counted in the state’s computation of its active science and mathematics teachers. One way of handling this would be to count teachers on the basis of their Full Time Equivalent (FTE) course load; a teacher who has a third of an assignment in mathematics and two-thirds in biology would count as one-third of a mathematics teacher and two-thirds of a biology teacher.

Ultimately, for all of these



Note

21

For an insightful discussion of the issue of multiple certifications and similar complicating factors, see Boe, E.E., & Gilford, D.M. (Eds.). (1992). Teacher Supply, Demand, and Quality: Policy Issues, Models, and Data Bases. Washington, DC: National Academy Press, pp. 153ff.).

complicating factors²¹ states simply must attempt to make appropriate adjustments in their calculations and in the protocols they employ to derive them.

Close Elaboration

2. Project the number of currently employed teachers in each mathematics and science discipline who are likely still to be teaching
   

   Note

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   For an aggregate estimate of teacher supply for the entire state, changes of teacher assignments from one school or district to another in the state are irrelevant. The only relevant consideration is whether teachers remain in the state teacher workforce or whether they retire, step out, or move to another state. Clearly, for an estimate of the teacher supply at the district level, teacher transfers out of the district are of critical importance.
   in the state²² (though not necessarily in the same school) in each of the next 5-10 years

Elaboration

Most states keep data on attrition and retirement rates of teachers over time. This is important because national data cannot capture the nuances of attrition in individual states, which include the impact of labor markets and retirement rules and incentives that vary from state to state and even from district to district. Ideally, state data will track rates of attrition over the years by teachers’ age and years of experience, and also by gender and race/ethnicity because attrition rates differ as a function of these factors.



Note

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For a review of several studies that discuss teacher attrition and retention, see Allen, M. 2005. Eight Questions on Teacher Recruitment and Retention: What Does the Research Say? Denver, CO: Education Commission of the States. For a recent analysis of teacher attrition patterns in Illinois, see DeAngelis, K.J., and Presley, J.B. (2007). Leaving Schools or Leaving the Profession: Setting the Illinois Record Straight on New Teacher Attrition. Carbondale, IL: Illinois Education Research Council. And for a more theoretical general discussion on teacher attrition, see Boe & Gilford (1992).

Some studies²³ indicate, for example, that the longer a teacher’s initial stay in teaching, and the older a teacher is (at least up to the age of around 40) before taking an initial break, the more likely the teacher is to re-enter the classroom.

Hopefully, states also will track the teacher attrition and re-entry patterns not only in science and mathematics generally but more specifically in chemistry, physics, etc., although at least



Note

24

Ingersoll, R.M., & Perda, D. (2009, March). The Mathematics and Science Teacher Shortage: Fact and Myth. Philadelphia: Consortium for Policy Research in Education, p. 36.

one recent study²⁴ based on nationwide data found no difference between the general attrition rate of secondary school teachers and the rate in science and mathematics specifically.



Note

25

Murnane, R.J., and Olsen, R.J. (1989). Will There Be Enough Teachers? The American Economic Review, 79, 242-246; and Alt, N.N., Henke, R.R., & Perry, K. (2007). To Teach or Not to Teach? Teaching Experience and Preparation Among 1992–93 Bachelor’s Degree Recipients 10 Years after College. Washington, DC: National Center for Education Statistics, p. 26.

Two other studies,²⁵ however, found that once high school science and mathematics teachers did leave teaching, they were the least likely of all teachers to re-enter the classroom.

Clearly, as the 2007-2010 economic downturn in the U.S. has demonstrated, economic realities have a significant impact on the extent to which such historical averages and trends can serve as a reliable basis for future teacher attrition or retirement projections.

Close Elaboration

3. Project the number of new science and mathematics teachers who are likely to be licensed and available to teach in each of the next 5-10 years

Elaboration

The two principal sources for newly licensed teachers in a state are the state’s teacher preparation programs (both traditional and alternate route programs) and the migration of teachers from other states or countries. Because it is the responsibility of a single agency in a state to grant new teacher licenses, it should be relatively easy to find out how many licenses are granted from year to year. Future projections can then be made on the basis of trends in the number of licenses issued over time – although such trends may not account for the expansion or addition of programs that prepare science and mathematics teachers or greatly expanded out-of-state recruitment efforts.

It is ultimately not sufficient, however, simply to project the number of new teacher licensees in science and mathematics over the next 5-10 years. Some of these teachers will leave the state to work elsewhere, some will teach in private schools, some will delay their entry into teaching, and some will pursue another career and never enter the K-12 classroom, at all. Thus, what is needed is an estimate of the number of new licensees who are likely to be available to teach in the next 5-10 years, and that is a far more difficult calculation.

One study from the National Center for Education Statistics (NCES) that offers some help in this direction is Alt, Henke, & Perry (2007), To Teach or Not to Teach? (pp. 31-36). The study involved a ten-year longitudinal survey of 1992-93 bachelor’s degree recipients, and the data provided make it reasonable to conclude that, at a minimum, approximately 13% of science, mathematics, and engineering graduates who received K-12 teacher licenses never taught. It might be possible, then, to subtract 13% of the number of newly prepared and certified science and mathematics teachers as a rough correction to the calculation of available new teachers in a given state, but the national data in the NCES study are not necessarily reflective of the labor market in individual states. Moreover, the study does not provide guidance in calculating the percentage of science and mathematics teachers who are delayed entrants, let alone what percentage of these delayed entrants should be considered candidates for teaching positions in any specific year.

In the end, all that such studies can do for any specific state is to provide some possible suggestions for how they might refine their estimates of the supply of science and mathematics teachers. And the studies clearly indicate that projections of teacher supply in individual states would benefit from careful state-level investigations – ideally in each local labor market – that can identify and quantify complex patterns of postponed entry and re-entry into teaching among science and mathematics teachers. These patterns not only become part of the basis for future projections but also can help in developing more effective recruitment and retention policies and practices.

Because of the many contingencies involved, it is also difficult to project the number of science and mathematics teachers who are likely to migrate into the state over the next 5-10 years and seek teaching licenses. Some states have aggressive out-of-state teacher recruitment programs, however, which may target and yield a reliable number of new teachers annually and also may be able to increase that number to respond to any projected shortfall.

Close Elaboration

4. Construct a first-order projection of the available supply of science and mathematics teachers statewide by adding the number of teachers estimated to be available over each of the next five years from the various sources and subtracting the number of teachers anticipated to be lost through attrition each year. This yields an actionable estimate that is based on the most dependable sources of teachers, though it lacks helpful additional refinements.

Refining the Projection

Beyond a first-order projection, which gives an approximate, statewide estimate of the available supply of science and mathematics teachers, it is ultimately desirable to develop a more sophisticated projection of the supply of teachers that includes other important factors and is more attuned to local realities. Several refinements would yield more precise and helpful supply projections – if data of adequate quality can be collected:

1. To the number of science and mathematics teachers who are currently employed, add the number of licensed science and mathematics teachers who applied for teaching positions in the current year (or year the data were collected) but were not hired.

Elaboration

If computed by district, the non-hired teachers can be counted as surplus even if they were eventually hired in another district or by private schools. If computed statewide, however, teachers can be counted as surplus only if they were not hired by any public school or district in the state. This will yield an estimate of the total available pool of science and mathematics teachers that counts only individuals who have demonstrated an actual interest in teaching – arguably a much more realistic estimate than one which attempts includes all licensed teachers in the state.

Close Elaboration

2. Calculate and subtract from the first-order supply projection the number of teachers who are currently teaching secondary science and mathematics courses but lack the appropriate state credentials

Elaboration

This limitation already should have been included in the first-order supply projection. Its repetition here emphasizes the importance of ensuring that only adequately qualified teachers are included in the calculation of the supply of science and mathematics teachers.

There is, however, no universally accepted definition of an “adequately qualified” teacher. And there is an additional challenge in finding a set of readily usable data points that would permit the easy identification of teachers' qualifications as adequate or inadequate in the kind of large-scale supply and demand analysis we are discussing here. For the sake of convenience and consistent with our focus in this project on teacher supply and demand, we would recommend that states consider a class as being taught by an “adequately qualified” teacher only if the teacher (a) is fully licensed or certified (i.e., not teaching on the basis of a temporary or emergency credential or waiver), or has demonstrated solid knowledge of his or her field and is enrolled in a teacher preparation program and pursuing a license; (b) is not teaching “out-of-field” – i.e., has the subject knowledge required by licensure or endorsement in the field to be teaching the class; and (c) is an actual employee of the school or district and not a temporary substitute.

To be sure, not all adequately qualified teachers are equally well-qualified or capable, and some teachers who are not technically qualified to teach a particular class may in fact be quite suitable for the task. A teacher who is a recent transfer from another state, for example, and has a temporary license because he or she needs to take a course or two to satisfy the new state’s licensure requirements is likely to do just fine. Moreover, the fact that a teacher is technically qualified to teach a class according to the criteria we have suggested does not guarantee that he or she will teach it well. As we discuss in the Teacher Quality and Teacher Licensure unit of the project, state licensure – especially licensure in the sciences – is a blunt instrument that does not necessarily ensure that teachers who meet the criteria for licensure and for teaching a particular subject are ultimately sufficiently well-qualified to be successful in teaching it. For purposes of conducting a statewide assessment of the adequacy of the teacher workforce, however, state licensure – if it is based on valid criteria and rigorously enforced – provides the analysis with an important quality control dimension.

Close Elaboration

3. To the extent possible, develop district-by-district supply projections.

Elaboration

The fact that there may be enough science and mathematics teachers available in the aggregate statewide does not mean that there will be enough teachers available for each school in each district. In some labor markets, there will be more than enough teachers to fill the positions available, while in other labor markets there will be too few. Teaching remains largely a



Note

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See Boyd, D., Lankford, H., Loeb, S., & Wyckoff, J. (2002, October). Understanding Teacher Labor Markets: Implications for Equity.

locally-based²⁶ profession, and many individuals simply will not accept teacher positions in communities where they do not wish to live or in schools at which they do not wish to teach even if there are no other teaching jobs available to them.

Good state-level projections will reflect these district variations, and a trend study of state projections based on solid data could make it possible to project the science and mathematics teacher supply for specific districts as a function of fluctuations in the overall state supply numbers. In the absence of such a trend analysis, or for districts that want even more accurate projections and a clearer understanding of the likely causes of and possible remedies for an estimated shortage of science and mathematics teachers, several kinds of specific data are required:

• Attrition rates (out of the district)
• Projected number of new and re-entering teachers
• Projected number of applicants for available positions
• Production estimates for preparation programs that are prime sources of a district’s teachers
• Information about the local “reserve pool” of science and mathematics teachers, including private school and retired teachers, that provides some indication of the number of teachers who may be enticed into teaching with various kinds of incentives

Close Elaboration

Exclusions

Excluded from the guidelines for developing teacher supply projection that were offered above are two other potential sources of teachers that are

Note

27

See, for example, the National Commission on Teaching and America’s Future report No Dream Denied; and Ingersoll and Perda (2009).

commonly cited²⁷ in discussions of teacher supply but that simply involve too much speculation to incorporate them into estimates that could claim reliability:

1. The entire reserve pool of science and mathematics teachers – the total number of individuals in the state who are certified to teach science and mathematics and who are not currently teaching in the public schools

Elaboration

It is impossible to know how many of these individuals are truly potential entrants into teaching. Those most likely to enter will be the delayed entrants or re-entrants already included in 3. above as well as private school teachers, whom research indicates have much higher rates of attrition than public school teachers and who possibly could be enticed into the public schools – though



Note

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See Luekens, M.T., Lyter, D. M., Fox, E.E., & Chandler, K. (2004). Teacher Attrition and Mobility. Results from the Teacher Follow-up Survey, 2000-2001. Washington, DC: National Center for Education Statistics.

likely²⁸ only a small percentage. The possibility of further increasing the number of entrants from this pool depends upon labor market conditions – or deliberate market manipulations through various kinds of incentives – and possibly upon the introduction of policies that provide such incentives or that allow retired teachers, for example, to re-enter teaching without sacrificing their retirement benefits.

For a variety of reasons we cannot assume, as



Note

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See, for example, Ingersoll, R.M., & Perda, D. (2009, March). The Mathematics and Science Teacher Shortage: Fact and Myth. Philadelphia: Consortium for Policy Research in Education.

some scholars²⁹ have suggested, that all science and mathematics teachers currently licensed in a state should be counted as being potentially available to teach:

• Many individuals who are prepared and newly licensed in a state move away to teach in another state
• Many others get teacher licenses as a backup in case they can’t find a job in their first-choice field of work
• Although individuals who have left the profession after an initial stint in the classroom may still be technically eligible to teach,
  

  Note

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  See for example DeAngelis, K.J., and Presley, J.B. (2007). Leaving Schools or Leaving the Profession: Setting the Illinois Record Straight on New Teacher Attrition. Carbondale, IL: Illinois Education Research Council.
  estimates³⁰ are that only one-third of them return.
• Although some retired teachers will return to teaching (not necessarily full-time) under the right conditions and circumstances, the number of retired teachers who return when state laws permit it is relatively small. In the state of Maryland in 2002-2003, for example, there were 913 re-employed retired teachers in the public schools out of a work force of over 55,000 classroom teachers. And Maryland has one of the
  

  Note

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  Conclusion based on data from the Common Core of Data for school year 2002-2003(NCES, 2005) and the Fiscal and Policy Note on House Bill 1254 Maryland Department of Legislative Services, 2004, Revised.
  more successful efforts³¹ to rehire retired teachers
• The fact that individuals are qualified, available, and even willing to teach doesn’t mean they will accept any teaching job offered them. For geographic, financial, or personal reasons, they may be willing to accept a position only in a limited number of schools and districts.

Close Elaboration

2. The greater scientific and technological workforce, which includes many individuals who have strong educational backgrounds in science or mathematics

Elaboration

Most of these individuals will never go into teaching. It is possible, however, to target specific incentives at this population to entice some of them into the classroom and give them training in pedagogy. How many individuals can thus be wooed into teaching depends upon the size and nature of the incentives and the realities of the larger labor market. Surveys of this population may provide an indication of the size of the incentives that would be required and thus inform a deliberate effort to recruit a certain number into the classroom – assuming that available resources and state and district teacher compensation policies permit it. An interest in teaching expressed in a survey, however, may not translate into a willingness to teach in actual fact.

Close Elaboration